Vessel, Motion Platform, Control System and Method for Compensating Motions of a Vessel

ABSTRACT

A vessel ( 1 ) including a motion platform ( 4 ), which platform comprises: —at least one carrier ( 6 ) for bearing, moving and/or transferring a load; —a gangway ( 16 ) provided with a first end pivotably connected to the carrier and an opposite second end; —a multiple number of first actuators ( 5   a ) for moving the carrier relative to the vessel; —a control system ( 8 ) arranged for driving the multiple number of first actuators, wherein a cable ( 20 ) extends from the vessel and/or the motion platform to at least a position at or near the second end of the gangway.

The invention relates to a vessel or an assembly for transferring peopleand/or loads between a vessel and a second vessel or structure. Theinvention further relates to a method for providing a gangway between avessel and a second vessel or structure.

Such a vessel is e.g. known from the International patent publication WO2007/120039. The vessel is provided with a motion platform whichcomprises a carrier borne by six hydraulic cylinders, and a movablegangway connected to the carrier for providing a connection between thecarrier and another structure, such as an offshore construction. Duringuse, with the aid of sensors, the motions of the respective vessel aremeasured. With the aid of these measurements, the orientation of thehydraulic cylinders is driven continuously so that the carrier remainsapproximately stationary relative to the fixed world. In this manner,motions of the ship are compensated so that a transfer between the shipand the fixed world, or vice versa, is made possible.

WO87/02723 discloses a vessel with an articulated ramp, comprising aramp section connected to a ship by means of a post, extendingperpendicular to and rotatable around a first axis perpendicular to adeck of the ship and pivotable relative to said post around a secondaxis perpendicular to said first axis. An outer ramp section isconnected to the first section by an intermediate platform which ismechanically kept in a position parallel to the ship's deck. The outersection can pivot relative to the first section around a third axisparallel to the first axis and a fourth axis perpendicular to said thirdaxis. Actuators are provided, by means of hydraulic cylinders, to movethe first and outer gangway sections relative to the ship and to an oilrig. Anchor lines extend below the ramp sections, from a set of constanttension winches in the post to a free end of the outer ramp section. Theanchor lines extend through a ball joint fixedly connected to the outerramp section by a rod, and through an anchor line stop fitting. The oilrig is provided with a mooring station for receiving the ball joint andthe anchor line stop fitting, by sliding the anchor lines between theball joint and the stop fitting into a slit in the mooring station andthen pulling the anchor lines tight, such that the ball joint is pulledagainst a first side of the mooring station and the stop fitting to anopposite side of the mooring station. In order to bring the stop fittingwith the anchor lines to the oil rig a pilot line is connected to theends of the anchor lines extending beyond the stop fitting. The pilotline is then passed to the oil rig by a rig man on the ship, which pilotman is received by a rig man on the oil rig. The rig man on the oil rigthen has to pull in the pilot line, to slide the anchor lines in saidslit. Then the winches are activated for bringing the anchor lines underload and subsequently pull the ball joint into a fixed connection withthe mooring station. In this known system there always has to be a rigman on the oil rig for coupling and uncoupling. In coupled condition theouter ramp section will rotate relative to the oil rig in six degrees offreedom around the ball joint, whereas all forces for maintaining thecoupled relationship are to be provided by the anchor cables extendingthrough said ball joint and the stop fitting.

FR2465640 discloses a system for transferring persons and small cargobetween a ship and an off shore structure, comprising a telescopinggangway carried by a platform on the ship. The platform allows passiverotation around an axis perpendicular to the ship's deck and limitedpivoting of the platform around an axis substantially parallel to saiddeck. The gangway is pivotably connected to the platform by a furtheraxis also extending substantially parallel to the deck. A hydrauliccylinder is provided between the platform and the first segment of thegangway connected to the platform, for compensating for part of theweight of the platform and for retracting the first segment of thegangway to a horizontal storage position. A cable extends below thegangway segments, tensioned by a constant tension winch provided belowthe first segment of the gangway, near the platform. A towing cable isprovided between a free end of the gangway and a boom of the off shorestructure. The boom is provided on a special platform of the structure,which allows the boom to pivot around a vertical axis over about 270degrees. A winch is provided for tensioning the towing cable, eitherfrom the gangway or the structure. FR2465640 does not disclose how thetowing cable is connected or disconnected from either the structure ofthe ship, and does not disclose how the towing cable is transferredbetween the ship and the structure, for coupling or decoupling. The endof the gangway is kept in closed contact with the structure bymaintaining the cables tensioned by means of the constant tensionwinches.

WO98/57845 discloses a system for transferring personnel and small cargobetween a vessel and an off shore structure, wherein the vessel isprovided with a large and complicated transfer device, comprising atelescoping gangway suspended from an articulated frame extending wellabove the gangway. Through the frame a pilot cable can be led fortransferring a ball joint coupling element to a complementary ball jointcoupling element provided on the off shore structure. In this structurethe gangway is passive and operated by means of the frame. The balljoint coupling provides for limited rotational movements of the gangwayrelative to the off shore structure.

WO2006/013342 discloses a ship with a gangway for providing a connectionbetween the ship and an off shore structure such as a windmill. To thisend a runway is provided, fixed on the ship, over which a first end ofthe gangway can be guided, between a stored position on the ship and anextended position. Guide wires can be provided between the ship and thestructure, over which guide wires the gangway can be guided to thestructure. The gangway is thereby supported by the guide wires and therunway and its free end can be supported at the off shore structure. Thecables are kept taut at all times during use and the first end will moveover the run way in order to compensate for movement of the shiprelative to the structure.

One of the objects of the invention is to improve a vessel including amotion platform.

Another object of the invention is to reduce manufacturing and/oroperational costs of a motion platform.

At least one of these and other objects are achieved with a vessel,assembly, platform and/or method according to the present description.

In a first aspect this disclosure can be characterised by a motioncompensation platform, which platform comprises at least one carrier forbearing, moving and/or transferring a load and a gangway provided with afirst end pivotably connected to the carrier and an opposite second end.A multiple number of first actuators is provided for moving the carrierrelative to the vessel, and a control system is arranged for driving themultiple number of first actuators. A cable extends from the vesseland/or the motion platform to at least a position at or near the secondend of the gangway. During movement of the gangway to and/or from thestructure the cable can in embodiments be carried by the gangway, forexample at or near the second end thereof.

In a second aspect this disclosure can be characterised by an assemblyof a vessel according to the invention and a mooring element, whereinthe mooring element comprises a counter coupling element for coupling tothe cable and/or to a coupling element connected to the cable.

In a third aspect this disclosure can be characterised by a motionplatform, particularly but not exclusively suitable for a vessel asdescribed, which platform comprises at least one carrier for bearing,moving and/or transferring a load, a gangway provided with a first endpivotably connected to the carrier and a second end for contacting atarget area, a multiple number of first actuators for moving the carrierrelative to the vessel. At least a second actuator is provided formoving the gangway relative to the carrier, whereas a control system isarranged for driving the multiple number of first actuators and fordriving the at least one second actuator. A cable is provided which isor can be carried at or near the second end of the gangway. The cablewill preferably at least be carried by the gangway during movement ofthe second end of the gangway towards or away from a second vessel orstructure with which the cable is to be connected.

In a fourth aspect this disclosure relates to a method for providing agangway between a first vessel and second vessel or a structure, such asan off-shore structure, wherein the gangway is carried at a first end bya motion platform on the vessel and has an opposite second end. Furthera cable is provided, connected to the vessel and/or the platform, forexample by a winch. The method comprises, but is not necessarily limitedto the steps of:

-   -   moving the gangway by the platform, preferably in an active        mode, such that the second end is brought to a position near or        in contact with the second vessel or structure;    -   connecting the cable to the second vessel or structure;    -   allowing the motion platform and/or gangway to follow the        movements of the vessel relative to the movements of the second        vessel or structure, especially by bringing the platform and/or        gangway from an active mode into an inactive mode.

In embodiments the cable is carried by the gangway to and from thestructure, and is preferably released from the gangway once it isconnected to both the vessel and the structure.

In clarification of the invention, exemplary embodiments of a vessel,motion platform, method and use according to the invention will befurther elucidated with reference to the drawing. In the drawing:

FIG. 1 shows a schematic perspective view of a vessel according to theinvention;

FIG. 2 shows a schematic diagram of the vessel shown in FIG. 1;

FIG. 3 shows a schematic perspective of a motion platform according tothe invention;

FIG. 4 shows a flow chart of an embodiment of a method according to theinvention;

FIG. 5A-K schematically a series of steps in providing and removing agangway;

FIG. 6A-D schematically steps of an alternative embodiment;

FIG. 7 in top view schematically an embodiment of an assembly of thepresent invention; and

FIG. 8A-D disclose an embodiment of a coupling element and countercoupling element for coupling a cable.

In this description, identical or corresponding parts have identical orcorresponding reference numerals. In the drawing, embodiments are givenonly as examples. The parts used there are mentioned merely an asexample and should not be construed to be limitative in any manner.Other parts too can be utilized within the framework of the presentinvention.

According to embodiments of the invention a gangway is or can be usedfor transferring a cable from a vessel to another vessel or structure,for providing a connection between the two. Then the cable and,optionally, the gangway and/or platform are used to keep the second endof the gangway, opposite the first end which is connected to theplatform, in close proximity off and preferably in contact with thesecond vessel or structure.

In this description reference is made to for example second vessels,structures such as off shore structures and the like, with which aconnection is to be made by a gangway of a vessel according to thisdisclosure. In this description second vessel and structure areinterchangeable, unless otherwise specified, and may both be referred toas structure 2.

In this description a gangway is to be understood as an element orassembly for transferring or allowing to transfer people, cargo, animalsor other loads between a vessel and another vessel or structure, thegangway bridging at least part and preferably all of a gap or distancebetween the vessel and the second vessel or structure or at least alanding area thereof.

In this disclosure a cable has to be understood as any element which isknown to be used or suitable for connecting a vessel to another vesselor structure, such as but not limited to metal, plastic or fibre cables,such as mooring cables or lines, chains, rods and the like. In thisdescription second vessel or structure has to be understood as includingbut not limited to sea going vessels and ships, hulls, off-shorestructures such as drilling platforms, windmills and the like, forexample permanently, semi-permanently or temporarily placed in and/or onopen water.

In this description a Stewart platform is described as the basis for amotion platform, by way of example only. Other types of motion platformscan be used within the context of the invention too.

FIG. 1 schematically shows an embodiment of a vessel 1 according to theinvention. With this vessel 1, a load such as for instance people,animals, goods and/or other loads can be transferred from the vessel 1to a target area, such as for example another, second vessel or astructure, such as for example an off-shore structure 2, and vice versa.The structure 2 can for example be a frame or base of, for instance, awindmill or platform at sea 3. For transfer, the vessel 1 is providedwith a motion platform 4. This platform can be designed to compensatefor motions of the vessel 1 relative to the structure 2, for the purposeof holding a part of the platform or connected elements contacting thestructure 2 relatively still relative to the structure 2, so that forinstance people such as windmill construction personnel can transferrelatively safely. The motions of the vessel 1 that can be compensatedmay comprise linear motions such as surge (vessel moves from front 1A toback 1B), heave (up and down) and sway (sideways), and rotating motionssuch as roll (bow from left to right) yaw (the vessel 1 rolls from leftto right) and pitch (bow up and down). Naturally, the motions of thevessel 1 are often combinations of these linear and rotational motions.

This transferring from or to the vessel 1 should of course not beunderstood as limited to the transfer from and/or to windmills 2. Inprinciple, transferring can be carried out between the vessel 1 and anyother surrounding structure or vessel 2. The vessel 1 is suited fortransferring, for instance, people, animals and/or loads to, inprinciple, any offshore construction, such as platforms at sea 3 and/orother constructions in the water 3, etc. In certain embodiments, avessel 1 according to the invention is designed for transferring to anypart connected to the fixed world, such as a quay, a levee, cliffs,steep rocks, (sea)floor etc. In certain embodiments, a vessel 1 has beenmade suitable for transferring to other moving elements and/or floatingelements, such as, for instance, other vessels. To that end, with theaid of, for instance, a camera, optical sensor or the like, the motionsof such a moving element can be registered and be compensated by theactive components of the platform.

In the embodiment shown, the motion compensation platform 4 is providedwith a carrier 6 and a multiple number of first actuators, implementedas six hydraulic cylinders 5 a, for moving the carrier. Such a motionplatform 4 is for example known as simulation platform, as “Stewart”platform. The carrier 6 can be designed to be movable in six degrees offreedom. However, the carrier can also be designed to be movable in lessdegrees of freedom, e.g. three degrees of freedom, e.g. with respect toroll, yaw and pitch. The platform 4 further comprises a gangway 16having a first end 16 a and a second end 16 b. The gangway first end 16a is pivotably connected to the carrier 6. Further, the gangway secondend 16 b, opposite the first end 16A is or can be brought into contactwith the structure 2. The gangway 16 can be moved with respect to thecarrier 6 by driving at least a second actuator 5 b provided by theplatform. In operation, during at least a certain period the second end16 b of the gangway 16 can be held substantially stationary relative tothe windmill 2 by actively driving the multiple number of hydrauliccylinders 5 a and the at least one second actuator. To that end, theplatform is further provided in a known manner with motion sensors and acontrol system for appropriately driving the respective actuators.

FIG. 3 shows a schematic perspective of a motion platform 4 according tothe invention. The platform includes a framework or base 50 rigidlyfixed to the vessel 1. The multiple number of first actuators 5 bear thecarrier 6 on the framework 50. The carrier 6 is provided with a topsurface 6 on which the gangway 16 is pivotably mounted via a pivotmechanism 25. Further, FIG. 3 shows the second actuator 5 b enabling thesecond end 16 b of the gangway 16 to be lifted and lowered with respectto the carrier 16. More specifically, the second actuator 5 b isarranged for pivoting the gangway 16 with respect to a first pivotingaxis A substantially parallel to the carrier 6 and transverse withrespect to a longitudinal axis L of the gangway 16. Thus, by pivotingthe gangway 16 around the first pivoting axis A, the second end 16 b ofthe gangway can be lifted or lowered to follow a target height of thetarget area 2.

The platform is further provided with another second actuator (notshown) that is arranged for pivoting the gangway 16 with respect to asecond pivoting axis B substantially transverse with respect to theplane wherein the carrier 6 extends, so that the gangway may swivelclockwise or counter-clockwise in a substantially horizontal plane or atleast in a plane or parallel to a plane perpendicular to said axis Band/or substantially parallel to the plane of the carrier 6.

The gangway includes a first gangway section 26 a and a second gangwaysection 26 b mutually interconnected via a translation mechanism 28. Thefirst gangway end 16 a is provided on the first gangway section 26 a,while the second gangway end 16 b is provided on the second gangwaysection 26 b. The platform is further provided with a second actuator,e.g. integrated in the translation mechanism 28, for moving the secondgangway section 26 b with respect to the first gangway section 26 asubstantially along the gangway longitudinal axis L, so that the gangwaysecond end 16 b may follow a lateral, horizontal movement of the vesselwith respect to the target area 2. The gangway 16 can thus be extendedand retracted by means of the mechanism 28 and the relevant secondactuator.

In embodiments by compensating a vessel movement via actively drivingsome or all second actuators 5 b, a motion compensation in three degreesof freedom can be performed such that the carrier 6 has to compensatefor the other three degrees only. In embodiments compensation, as far asnecessary, can be performed in more than three, for example four, fiveor all of the six degrees of freedom by actively driving the firstactuators.

It is noted that in another embodiment of the motion platform accordingto the invention, another design can be implemented, e.g. having onlytwo second actuators or only one second actuator for the gangwayextension and retraction. Then, the carrier has to perform a motioncompensation in more degrees of freedom, e.g. four degrees or fivedegrees of freedom.

FIGS. 1 and 2 show a cable 20, at a first end connected to the vessel 1by a winch 21. In embodiment such winch can be a standard winch or canfor example be an auto recovery winch, render and recovery winch orconstant tension winch. An opposite second end of the cable is connectedto the structure 22 by a coupling element 23, connected releasably to acounter coupling element 24 on the structure 2. The counter couplingelement 24 can be formed by or part of a mooring element 25 as will bediscussed. With the cable 20 the distance between the vessel and thestructure can be defined, at least maximised, and/or controlled bydefining the length X of the cable 20. The tension in the cable 20 canbe adjusted and/or controlled, for example by the winch 21, and thecable 20 can be pulled taut.

In embodiments the gangway 16, especially the second end 16 b thereofcan be held by and/or pushed against the structure 2, for exampleagainst, into and/or onto a mooring element 25. In embodiments thegangway, especially the second end 16 b can be kept in a relativelyconstant position relative to the structure 2, for example in, on and/orover the mooring element 25, as a result of the tension in the cablebeing controlled, especially kept taut and the platform 4 and/or thegangway 16 being controlled such that the end 16 b of the gangway 16 ispushed against the mooring element 25. In such embodiment the platform 4and/or gangway 16 can be controlled such that they only follow themovements of the vessel 1 in stead of compensating for the movementsthereof relative to the structure or second vessel 2. In embodiments inwhich the gangway 16 has two or more parts 26A, B movable relative toeach other in a length direction L of the gangway 16, such as forexample shown in FIGS. 3, 5, 6 and 7, the second end 16B can be held inposition relative to the structure or second vessel 2, especiallyrelative to a mooring element 25 thereon, by extending and reducing theaxial length of the gangway 16, by movements of the second part 26 brelative to the first part 26 a, and for example allowing the gangway topivot freely around the first pivot axis A and/or second pivot axis Band/or for example by holding the platform in a fixed position or byallowing the platform to follow movements of the gangway substantiallypassively. Substantially passively or not active can be understood inthis context as including but not limited to allowing the platform,especially the carrier to follow movements of the first end of thegangway 16 by not actively controlling the pressure of the firstactuators 5 a, and/or by actuating the first actuators 5 a only to suchextend that the platform 4 does not pull the second end 16 b away fromthe structure or second vessel 2. In embodiments the cable 20 can becontrolled such that the majority or even all of the movements of thevessel 1 relative to the structure or second vessel 2 can be compensatedfor by adjustments in the length of the gangway 16 between the first andsecond ends 16 a, 16 b and pivoting of the gangway 16 relative to theplatform 4, especially the carrier, for example around the first and/orsecond axis A, B. Such pivoting can be free pivoting, e.g. withoutactuation by any second actuator, or can at least partly be controlledby at least one second actuator 5 b. In all of these embodiments thefirst and/or second actuators 5 a, 5 b could be controlled to forexample dampen movements of the parts of the platform and/or gangwayrelative to each other and/or relative to the vessel 1.

In embodiments a vessel, especially a platform 4 with a gangway 16 canbe used in two modes: an active mode for transferring an end of thecable 20 and/or the second end of the gangway 16 from the vessel 1 to astructure or second vessel 2 to which a connection is to be made, and asecond mode in which the platform is operated more passively than inactive mode, and at least partly follows movement of the gangway anddoes not compensate for the movements of the vessel or at leastcompensates for movements of the vessel to a lesser extend than inactive mode. In active mode at least the first actuators 5 a andpreferably also second actuators 5 b can in embodiments be controlledactively, based on the sensor signals of sensors 7, as discussed withrespect to and in the prior art as for example disclosed in WO2007/120039 and/or WO2012/021062, for actively compensating formovements of the vessel 1 and bringing and holding the second end 16 bin a preferred position relative to the structure or second vessel 2. Inpassive mode the position of the second end 16 b of the gangway is notcontrolled, or at least not only actively controlled by movements of theplatform and/or actuation of the first and second actuators 5 a, 5 b,but at least partly effected by the fact that the vessel 1 is kept at arelatively fixed distance from the second vessel or structure 2 by thecable 20, such that the second end 16 b of the gangway 16 can be keptsubstantially in a preferred position relative to the second vessel orstructure 2 without the necessity of fully compensating for themovements of the vessel 1 relative to the second vessel or structure 2.This allows for a far less complicated system to be used, which can forexample have a lighter platform 4, smaller actuators 5, a smallerhydraulics or pneumatic or electrical system for driving the actuatorsand/or, less complicated sensors. In embodiments a vessel 1, assembly,or platform according to the description can moreover enhance safety,since even if the platform 4 is not actively controlled by the system,for example due to power failure, the second end 16 a can be kept inclose proximity of the second vessel or structure, for safe transfer offor example persons and/or cargo.

FIG. 2 shows a schematic diagram of the vessel 1. The control system 8is connected to the motion sensors 7 for receiving motion sensor data,for instance the rocking of the vessel 1 in the water 3. With the aid ofthese measurement data, during use, at least in active mode, a firstdriving signal and a second driving signal are generated for driving thehydraulic cylinders 5 a and the at least one second actuator 5 b,respectively, for moving the carrier 6 with respect to the vessel 1 andfor moving the gangway 16 with respect to the carrier 6, respectively,in order to bring and at least temporarily maintain the second end 16 bof the gangway substantially stable relative to the target area. Inorder to generate the driving signals, the control system 8 is providedwith processor 13. The control system also includes a memory 14.Processing these measurements and actively driving the hydrauliccylinders 5 a and the at least one second actuator 5 b is a task to beperformed by the control system 8.

The actuators 5 a, 5 b may include pneumatic and/or hydraulic means,linear motors, electric driving elements etc. In the embodiments shownin FIG. 1, the pneumatic means 9 comprise at least one pneumaticcylinder 10 which is placed approximately in the centre of the motioncompensation platform 4 and is connected via pipes 15 to a pressurecompensator in the form of an accumulator 11 for buffering compressedair, and a compressor 12 for compressing air. After filling withcompressed air in the pneumatic cylinder 10 and the accumulator 11,after provision of a load, the cylinder 10 will remain pressurized andit can continue bearing at least a part of the load. The pneumaticcylinder 10 may have the property of passively moving along in itslongitudinal direction. Motions of the carrier 6 in the longitudinaldirection of the cylinder 10 are followed by compression and expansionof the air in the cylinder 10 and the accumulator 11. Small pressurelosses in the pneumatic cylinder 10 through, for instance, friction canbe measured and compensated with the aid of, for instance, thecompressor 12 and/or the control system 8. Such pneumatic means 9 areknown per se from the so-called ‘heave compensation’ systems. By placingthis longitudinal direction in the direction of gravity, a great force,e.g. that of the weight of the carrier 6 and the load, will becontinuously absorbed by the passive pneumatic means 9, and hence alsoin the case of a defect in the active elements of the motioncompensation platform 4 such as, for instance, the sensors 7, thecontrol system 8 and/or the hydraulic cylinders. In particularembodiments, the pneumatic means 9 are advantageously placed in otherdirections, for instance for compensating tilting motions of the carrier6 after, for instance, a defect. In this way, upon a defect of anelement such as a cylinder 5, the pneumatic means 9 can prevent themotion compensation platform from making a relatively unsafe motion,such as, for instance, collapsing. Defects that might occur are, forinstance, power supply failure or valves in the active hydraulic systembecoming wedged. Naturally, also, other, preferably passive, pressuresystems 9 can be utilized within the framework of the invention. Incertain embodiments, instead of and/or in addition to pneumatic means 8,that is the cylinder 10, at least one spring can be utilized as passiveelement 10, for instance a spiral and/or gas spring. The pneumatic means9 can, in principle, comprise different types of pressure elements suchas, for instance, hydraulic means and/or elastic means and/or a pullingelement, etc. Naturally, one or more pressure elements can be utilized.Depending on, for instance, the expected use, desired precision and/oreconomic considerations, one particular type, one particular amountand/or positioning can be selected. A passive pressure system 9 providessecurity in that it will, in principle, not fail and can remainfunctional without continuous actuation. Also, such a passive system 9can remain of limited complexity. In embodiments no such pneumatic meansare provided or they are designed differently, for example hydraulic.

In particular embodiments, the motion sensors 7 comprise known motionsensors 7 such as for measuring motions of the vessel 1, for instanceaccelerometers or dynamometers. With known accelerometers, the motion ofthe vessel 1 relative to the fixed world can be measured. Also, inparticular embodiments, other types of sensors 7 can be utilized, suchas for instance cameras, GPS (Global Positioning System), sensorsutilizing electromagnetic waves, sonic waves, etc. The sensors 7 maymeasure the position of the vessel 1 relative to one or more elements inthe surrounding area, such as for instance towards another vessel 1and/or the fixed world. The information the control system 8 receivesfrom the motions sensors 7 is processed via, for instance,pre-programmed algorithms so that the actuators 5 a, 5 b can be drivenfor holding the second end 16 b of the gangway 16 approximatelystationary relative to the target area 2. In passive mode preferably atleast the second actuator 5 b for extending and retracting the gangwayis actively controlled, for example advantageously only that secondactuator.

Advantageously, the motion sensors include orientation sensors andsensors for measuring a relative distance towards the target area, sothat another orientation and/or another position can be measured,thereby avoiding the use of absolute position sensors. As a result, themotion sensors can be implemented in a relatively cheap manner.

The measurements may further include providing measurement dataperformed from another structure, e.g. another vessel, concerningmovements of the vessel at hand. Measurements may also include providinglaser data or video data to retrieve relative position data.

In this respect it is noted that the use of orientation sensors andsensors for measuring a distance towards the target area can not only beapplied with the method according to the description, but also, moregenerally, in combination with a method for compensating motions of avessel, comprising the steps of measuring motions relative to at leastone element in a target area and driving a multiple number of firstactuators for moving a carrier relative to the vessel.

The measurements may include providing sensor data of motions of thevessel, the platform and/or the gangway, preferably the second end ofthe gangway, relative to the target area 2. In particular, verticalposition data of the second end 16 b of the gangway can be obtained bymeasuring the height of said gangway second end 16 b relative to thetarget area 2, thereby enabling the control system 8 to follow thetarget area height relatively easily and accurately by driving thesecond actuator controlling pivoting the gangway relative to the firstpivoting axis A.

The operation of an embodiment of the motion platform 4 is in generalapproximately as follows. When the vessel 1 is close to the structure orsecond vessel 2, the platform 4 is activated in active mode. Vesselmotions are measured via the sensors 7, which measurement data is usedas input for the control system 8. In response to the measurement data,a first driving signal and a second driving signal is generated fordriving the respective actuators. Through continuous adjustment of theactuators 5 a, 5 b the gangway second end 16 b will be able to virtuallystand still relative to the structure 2, at least temporarily. The cable20 is transferred to the structure or second vessel 2 preferably by thegangway 16, and is coupled to the second vessel or structure 2, forexample by the coupling element 23 and counter coupling element 24and/or mooring element 25. Then the cable 20 is released from thegangway 16 and pulled taut by the winch 21. The second end 16 b of thegangway is preferably pushed against the second vessel or structure 2,especially to a mooring element 25. The platform is brought in passivemode, or fixed in a position. In this position persons, loads, animalsand the like can safely be transferred from the vessel 1 to the secondvessel or structure 2 or vice versa.

Coupling element 23 and counter coupling element 24 can be any knownsuitable set of cooperating coupling elements, such as for example hookand eye, loop and boulder, magnets, or any such elements known in theart and suitable for making a reversible connection. In FIGS. 5 and 6 byway of example only a hook is shown as coupling element 23, whereas aneye (not shown) is used as counter coupling element 24.

In FIG. 8A-D an embodiment is shown of a coupling element 23 connectedto a cable 20 and a counter coupling element 24 for cooperationtherewith. In FIG. 8A-D schematically steps of a sequence for coupling acable 20 to a structure 2 such as an off shore structure are shown. Asis shown in FIG. 8A schematically a first coupling element 23 can beprovided having basically a hook shape or anchor shape. It can have acentral leg 34 and a first and a second prongs 35, 36, one on eitherside of the central leg 34. The cable 20 can be connected to the freeend of the leg 34. In this embodiment the end 16B of the gangway 16 isprovided with a rod 37 over which a first prong 35 can be hooked, forcarrying the first coupling element 23 towards the structure 2. On thestructure 2, preferably at or near a mooring element 25, if applicable,the second coupling element 24 is provided, comprising a second rod 38.As is shown in FIG. 8B the second prong 36 can be moved over and hookedto the second rod 38 by manipulating the element 23 by movement of thegangway 16. In FIG. 8B the element 23 is shown, hooked over both rods37, 38.

Once the second prong 36 has been hooked over the second rod 38, thegangway end 16B can be retrieved slightly, such that the first rod 37 ispulled away from the element 23, out from under the first prong 36, asis shown in FIG. 8C. The cable 20 is now connected to the structure 2,especially to the element 24. Then the cable can be tightened by thewinch 21, and the end 16B, especially the platform 31 can be moved intothe space 29 of the element 25 through the opening 29A as described, forproperly coupling the gangway with the structure 2.

Should the cable 20 be released, the same sequence can be performed, inreversed order. Preferably the rods 37 and 38 are positioned such thatthey do not interfere with a proper functioning of the coupling betweenthe gangway 16 and the element 25 as described. For example the rods 37,38 can be placed to a side of the gangway 16, or spaced slightly apartfrom the edge 32 of the platform 31, e.g. closer to the first end 16A ofthe gangway, such that the rod 37 does not enter into the space 29.

Obviously other coupling elements 23, 24 can be used, or differentlyshaped. For example the element 23 can have more than two prongs, forexample three or four, as used in a grapnel or grapples or grappleirons, dredging hooks and the like.

This coupling as shown in FIG. 8 releases the cable automatically fromthe gangway 16, preventing undesired and excessive forces acting on thegangway and/or on the cable 20. More in general it may be preferable torelease the cable 20 from the gangway once the cable has been properlyconnected to the structure 2 for that purpose.

Since the platform 4 and the gangway 16 can be actively controlled, theend 16 and thus the first coupling element 23 can be positionedaccurately and relatively easily with respect to the second couplingelement 24, without the necessity of using a pilot line or the like tobe transferred separately from the ship 1 to the structure 2 or viceversa, as is shown in the prior art. The cable 20 can be coupleddirectly and accurately. Whereas the cable can be released from thegangway 16 easily after coupling. The cable 20 and the gangway can thencooperate in holding the gangway end 16B in the proper position relativeto the structure 2.

When releasing the gangway 16 from the second vessel or structure 2 theplatform 4 is brought into active mode again, whereas the cable isreleased from the second vessel or structure 2 and, if applicable,coupled to the gangway again. Then the gangway is retracted and/orrotated and/or pivoted back onto the first vessel 1.

In FIG. 5A-K schematically a series of steps is shown in providing agangway 16 between a vessel 1 and a second vessel or structure 2. InFIG. 5A the platform 4 is shown in a stable state, with the gangway 16pivoted down, such that the second end 16 b thereof rests on the deck 27of the vessel 1. An operator P can mount the platform 4 via the gangway16. On the left hand side of the FIG. 5A-K schematically part of astructure 2 is shown, which by way of example comprises a central column2A and a deck 2B. On the deck 2B a mooring element 25 is mounted, forexample bolted to the deck 2B. The mooring element 25 has an in top viewsubstantially triangular catching space 29 having an opening 29 a opentowards the side of the vessel 1 or at least an edge of the deck 2B,into which the second end 16B of the gangway 16 can be inserted. Thespace 29 is provided at a top side thereof with two guide flanges 30extending inward from two opposite sides of the space 29. The second end16B comprises a plate or platform element 31, for example having asubstantially semi circular edge 32. The plate or platform element 32can be inserted into the space 29 such that it is at least partlyenclosed below the flanges 30, such that it cannot be removed from thespace 29 in any direction other than through the opening 29A. Thus thesecond end 16B can be enclosed within the space 29 in all but onedirection.

In FIG. 5B the operator P has mounted the platform 4 and will actuatethe system such that the end 16B of the gangway 16 is lifted from thedeck 27. FIG. 5C shows the platform 4 with the gangway 16 having beenrotated over an angle of about 180 degrees from the position in FIG. 5B,such that the second end 16B faces the structure 2. In this position theplatform 4 can still be in a fixed position, i.e. not in an activeposition compensating for movements of the vessel. In for example thisposition the system can be brought in active mode, such that theplatform 4 will start compensating for the movements of the vesselrelative to the structure 2, especially relative to the mooring element25. As shown in FIG. 5D the operator P can actuate a second actuator 5 bsuch that the second part 26B of the gangway 16 is moved forward, i.e.such that the gangway 16 in the direction L is extended, bringing thesecond end 16B closer to and in contact with the mooring element 25. Thecable 20 is allowed to follow the relative movement of the second end 16b, such that the coupling element 23 is brought to the mooring element25 by the gangway 16. As shown in FIG. 5E the second end 16B, especiallythe plate or platform element 32 is pushed into the space 29. Thecoupling element 23 can be coupled to the counter coupling element 24,and the cable can be pulled taut by the winch 21.

When or after the cable 20 has been properly coupled to the structure orsecond vessel 2, the platform can be brought out of the active mode, forexample into the inactive mode. Preferably the gangway 16, especiallythe second end 16B thereof is actively pushed into the space 29,preferably by actuating the relevant second actuator 5 b used forextending and retracting the gangway 16 in length direction. This can bedone by moving the second part 26B relative to the first part 26A in thelength direction L. Alternatively the platform can be used for providingsufficient pressure to the gangway, for example by partly actuating atleast one of the first actuators. As is shown in FIG. 5F then astaircase 33 can be mounted to the platform 4, for easy access to andfrom the carrier 6, off the deck 27. Since the platform can be keptstationary relative to the deck 27 this is very easily done. As is shownin FIG. 5G a person P2 can easily move over the gangway 16 to thestructure 2 or return from the structure 2 to the vessel 1. During suchtransfer preferably the gangway 16, especially the second end 16B ispushed against the mooring element 25, into the space 29, whereas thecable 20 is kept taut. In embodiments the gangway 16 is allowed tofreely pivot around the first axis A relative to the platform 4, or atleast the carrier. In embodiments the carrier 6 or at least the gangway16 can pivot freely around the second axis B as well.

Preferably the space 29 in side view also has a substantially triangularshape or at least widens towards the opening 29A, such that the platformelement or plate 32 can pivot within the space 29 over an angle α aroundan imaginary axis C parallel to the deck 2B and to the opening 29A,whereas preferably the space 29 and the platform element or plate 32 aredesigned such that the platform element or plate 32 can pivot within thespace over an angle 13 around an imaginary axis D (FIG. 7) perpendicularto the deck 2B and the axis C, in order to allow the gangway to pivotrelative to the structure 2 too. Alternatively or additionally themooring element 25 could be mounted to the structure 2 such that it canpivot relative to the structure 2. Thus the gangway 16 can followrelative movements of the vessel, with the platform in a fixed positionor at least in a mode in which it not fully compensates for the relativemovements of the vessel 1.

FIG. 5 H-K show schematically steps of retracting the gangway 16. InFIG. 5H the staircase is removed, the platform 4 is brought back intoactive mode and the cable 20 is slackened and released from thestructure by releasing the coupling element 23 from the counter couplingelement 24. The cable is again supported by the gangway 16, for exampleby coupling the coupling element 23 to the gangway or in any othersuitable way. Then the second end 16B is retracted from the space 29 inthe mooring element 25, as is shown in FIG. 5I, for example byretracting the gangway 16 and/or by movement of the platform 4. Then theplatform may be brought out of the active mode again and can for examplebe settled into a neutral position, as is shown in FIG. 5J. From thisposition the gangway 16 can be rotated over 180 degrees again, forexample by rotating the carrier 6, back above the deck 27 whereafter thegangway can be brought into the position as shown in FIG. 5K, allowingthe operator P to leave the platform over the gangway 16.

During retracting the gangway 16 the cable may be rewound onto the winchor otherwise retrieved too.

In FIG. 6A-D steps of an alternative method are shown, wherein themooring element 25 is carried to the structure 2 by means of the gangway16. In this embodiment with the platform 4 as shown in FIG. 6A themooring element is mounted onto the second end 16B of the gangway 16,for example by sliding it with the space 29 over the plate or platformelement 32 or just the end 16B. On the structure 2 people P3 may beavailable for assistance. As described before, with the platform not inactive mode, the gangway 16 is brought in a position above the deck andis then rotated outward, to the position shown in FIG. 6B, in which theplatform may be switched into active mode. The cable 20 may already beconnected to the mooring element, for example using coupling and countercoupling elements 23, 24, or otherwise. In embodiments the cable 20could even be fixedly connected to the mooring element 25. From theposition in FIG. 6B the second end 16B with the mooring element isbrought to the structure 2, especially to a deck 2B or such surface formounting the mooring element 25. The cable is released to allow for suchmovement of the mooring element end/or second end 16B.

FIG. 6D shows the position in which the mooring element 25 has beenplaced on the structure 2, with the platform still in active mode. Thepersons P3 on the deck 2B of the structure 2 can mount the mooringelement 25 properly to the structure, permanently or temporarily, forexample by bolting, screwing, welding, magnets, form fitting elements,or any other suitable elements or means. During the mounting of themooring element 25 the platform 4 is preferably kept in active mode,such that no undesired forces are exerted on the mooring element by thegangway during mounting. Once the mooring element 25 has been properlyplaced and, where necessary, the cable 20 has been attached to thestructure 2 and/or mooring element 25 and has been tensioned, such aspulled taut, the platform 4 could be brought out of the active mode.

When retracting the gangway 16 again, for example after it has completedit's function with respect to the structure 2, the mooring element 25could be left in position on the structure 2, for example for future usein combination with the vessel or a similar vessel. Alternatively themooring element 25 could be released from the structure 2 and retractedwith the gangway 16 for further use with the same or other structures 2.A mooring element 25 can be provided with appropriate connectingelements, such as pins, screws, bolts, rivets, holes or openings,magnets or any such means for connecting the mooring element 25 to thestructure.

In FIG. 7 in top view schematically a mooring element 25 is shownmounted on the second end 16B of the gangway 16, for carrying themooring element 25 to or from the vessel form or to the structure 2. Ascan be seen the mooring element 25, especially the space 29 can be opentowards a top side of the element 25, between the flanges 30. However,such element 25 could also be closed to the top side 34, and could bedifferently shaped and/or dimensioned. In other embodiments the mooringelement 25 could be designed to fit within the second end 16B of thegangway, for example by providing an opening in the plate or platformelement 32 which can be placed over the mooring element, for exampleforming more or less a ball joint type connection.

The method for compensating motions of a vessel can at least partly beperformed using dedicated hardware structures, such as FPGA and/or ASICcomponents. Otherwise, the method can also at least partially beperformed using a computer program product comprising instructions forcausing a processor of the computer system to perform the abovedescribed steps of the method according to the invention. Processingsteps can in principle be performed on a single processor, in particularsteps of providing first and second driving signals for driving themultiple number of first actuators and the at least one second actuator.However, it is noted that at least one step can be performed on aseparate processor, e.g. a step of receiving motion sensor data ofmotions relative to at least one element in a target area.

In a system and method of the present invention the gangway can inembodiments be actively operated, i.e. be in an active mode, meaningthat the relevant second actuator or actuators can actively move thesecond end of the gangway relative to the platform cq carrier thereof,for example by extending or retracting the gangway and/or changing theangle between the gangway and the platform cq carrier thereof. Inembodiments the gangway can be brought into a passive mode, in which theor each second actuator for operating the gangway is or can be passive,meaning that the length and/or position of the gangway is definedpassively by the relative position of the vessel and the secondstructure or vessel, wherein the length variations and/or anglevariations are provided for at least mainly by pulling and/or pushingforces exerted on the gangway by the vessel and/or structure or secondvessel. In embodiments a main aspect can be defined at least by using agangway for transferring a connecting cable from a vessel to a structureor second vessel.

The invention is by no means limited to the embodiments specificallyshown in the drawings and/or discussed in the description. Manyvariations thereof are possible within the present invention, includingbut not limited to all combinations of individual or groups of featuresas disclosed. The gangway can be connected differently to the platform,for example by means of a different hinging structure, such as aconnection which allows pivoting around different axis. The gangway canhave more than two moveable parts, or only one, and can be connected tothe platform 4 such that it can move in the longitudinal direction ofthe gangway relative to the platform, especially the carrier thereof,for at least partly compensating for movements of the vessel relative tothe structure. The mooring element can be omitted on the structure, orcan be an integral part thereof. The mooring element can be designeddifferently, as long as it allows for a connection with the platformsuch that the gangway can apply a force to the mooring element,preferably at least a pushing force against the mooring element. Theplatform can be designed differently, for example with a differentnumber of actuators and/or different types of actuators. The secondactuator for extending and retracting the gangway can be designed in anyappropriate way, such as for example but not limited to a hydraulic,pneumatic or electric piston-cylinder system, a spindle motor, a cablewith winch or any such suitable means known in the art, or combinationsthereof, for example enhanced safety. In stead of or additional to thecable a more rigid connector could be used between the vessel and thestructure, such as for example but not limited to a pole. In theembodiments shown the winch is provided on the deck of the vessel. Inother embodiments the winch could be connected to the platform, forexample to a base thereof. The cable can also be connected to the vesseland/or to the platform in a different manner, for example to a clamp,boulder or other such means known in the art. In alternative embodimentsadditionally or alternatively the winch or a winch can be placed on thestructure, to be used for forming a cable connection between the vesseland the structure. Such winch can for example be a winch alreadyavailable. Alternatively and/or additionally a crane or other hoistingdevice could be used for transferring the cable and/or the mooringelement from the vessel to the structure and/or vice versa and/or forforming the cable connection. In the embodiments shown and discussed theplatform is operated at least partly by a human operator on theplatform. It shall be clear that it will also be possible to operatesuch platform remotely, for example from a cabin or from the deck of thevessel or from the structure or even from further away, such as from ashore.

In embodiments the motion platform can be moved actively while movingthe second end of the gangway to the second vessel or structure, whereasthe motion platform is allowed to passively follow the relativemovements of the vessel after coupling the cable and/or the second endof the gangway to the second vessel or structure and/or the motionplatform can be moved actively while moving the second end of thegangway to the second vessel or structure, whereas the gangway isallowed to passively follow the relative movements of the vessel aftercoupling the cable and/or the second end of the gangway to the secondvessel or structure. The motion compensation platform can comprise or beformed by a Stewart platform with hydraulic, pneumatic and/or electriccylinders, as is known in the art.

In embodiments disclosed herein the platform can be brought from anactive mode to an inactive mode and vice versa. In embodiments theinactive mode could be designed such that in such mode the platform isin a fixed position, for example a rest position wherein the firstactuators are kept in a fixed length. In embodiments an inactive modecan be designed such that the platform, especially the carrier can stillmove by length adjustments of one, some or all of the first actuators,but either not actively controlled by the system or controlled to anextend that the platform does not compensate for movements of thevessel, for example for dampening movements resulting from shock or loaddifferences.

These and many other variations and combinations should be consideredalso having been disclosed herein.

1. A vessel including a motion platform, which motion platform comprises: at least one carrier for bearing, moving and/or transferring a load; a gangway provided with a first end pivotably connected to the carrier and an opposite second end; a multiple number of first actuators for moving the carrier relative to the vessel; a control system arranged for driving the multiple number of first actuators, wherein a cable extends from the vessel and/or the motion platform to at least a position at or near the second end of the gangway.
 2. The vessel according to claim 1, wherein the cable is connected to the vessel or the motion platform by at least a winch.
 3. The vessel according to claim 1, wherein the cable is provided with a connecting element at an end opposite the vessel and/or motion platform, for connecting to another vessel or structure.
 4. The vessel according to claim 1, wherein at least one second actuator is provided for moving the gangway relative to the carrier, wherein the control system is also arranged for driving the at least one second actuator.
 5. The vessel according to claim 4, wherein the control system is arranged for compensating a motion of the vessel in at least one degree of freedom by driving the at least one second actuator.
 6. The vessel according to claim 1, wherein at least one second actuator is arranged for pivoting the gangway with respect to a first pivoting axis substantially transverse with respect to a longitudinal axis of the gangway.
 7. The vessel according to claim 1, wherein at least one second actuator is arranged for pivoting the gangway with respect to a second pivoting axis substantially transverse with respect to the carrier.
 8. The vessel according to claim 1, wherein the first gangway end is provided on a first gangway section, wherein the second gangway end is provided on a second gangway section, and wherein at least one second actuator is arranged for moving the second gangway section with respect to the first gangway section substantially along a gangway longitudinal axis.
 9. The vessel according to claim 1, wherein the motion compensation platform comprises a Stewart platform with at least one of hydraulic, pneumatic or electric cylinders.
 10. An assembly of a vessel according to claim 1 and a mooring element, wherein the mooring element comprises a counter coupling element for coupling to the cable and/or a coupling element connected to the cable.
 11. The assembly according to claim 10, wherein the mooring element is provided with a receptacle for receiving the second end of the gangway, within and/or over the receptacle.
 12. The assembly according to claim 10, wherein the second end of the gangway and the mooring element are configured such that the mooring element can be carried by the gangway during movement thereof relative to the vessel.
 13. The assembly according to claim 10, wherein the mooring element is provided with connecting elements for connecting the mooring element to a vessel or structure.
 14. A motion platform, for a vessel as described in claim 1, which motion platform comprises at least one carrier for bearing, moving and/or transferring a load, a gangway provided with a first end pivotably connected to the carrier and a second end for contacting a target area, a multiple number of first actuators for moving the carrier relative to the vessel, at least a second actuator for moving the gangway relative to the carrier, a control system arranged for driving the multiple number of first actuators, wherein the control system is also arranged for driving the at least one second actuator, and wherein a cable is provided which is or can be carried at or near the second end of the gangway.
 15. A method for providing a gangway between a first vessel and second vessel or a structure, wherein the gangway is carried at a first end by a motion platform on the first vessel and has an opposite second end, wherein further a cable is provided, connected to the second vessel or structure, comprising the steps of: moving the gangway by the motion platform in an active mode, such that the second end is brought to a position near or in contact with the second vessel or structure; connecting the cable to the second vessel or structure; allowing the motion platform to follow the movements of the first vessel relative to the movements of the second vessel or structure, by bringing the platform from an active mode into an inactive mode and/or allowing the gangway to follow the movements of the first vessel relative to the movements of the second vessel or structure, by bringing the gangway from an active mode into an inactive mode.
 16. The method according to claim 15, wherein the cable during transfer to and/or from the second vessel or structure is carried by the gangway and the cable is released from the gangway after connecting the cable to the second vessel or structure, and is pulled taut, before allowing the motion platform to follow the relative movements.
 17. The method according to claim 15, wherein the motion platform is moved actively while moving the second end of the gangway to the second vessel or structure, whereas the motion platform is allowed to passively follow the relative movements of the vessel after coupling the cable and/or the second end of the gangway to the second vessel or structure.
 18. The method according to claim 15, wherein the motion platform is moved actively while moving the second end of the gangway to the second vessel or structure, wherein the gangway is allowed to passively follow the relative movements of the vessel after coupling the cable and/or the second end of the gangway to the second vessel or structure.
 19. The method according to claim 15, wherein after coupling the cable to the second vessel or structure, the cable is pulled taut, wherein the second end of the gangway is pushed against the second vessel or structure, at least partly by pushing a second part of the gangway in a length direction of the gangway away from the platform.
 20. The vessel according to claim 1, wherein the cable is provided with a connecting element at an end opposite the vessel and/or motion platform, for connecting to another vessel or structure, wherein the connecting element comprises at least a first prong for hooking over an element connected to the gangway and at least a second prong for hooking over a coupling element provided on the other vessel or structure, and wherein the element connected to the gangway is rod shaped and wherein the coupling element provided on the other vessel or structure is rod shaped.
 21. The method according to claim 15, wherein the cable is provided with a connecting element at an end opposite the vessel and/or motion platform, for connecting to another vessel or structure, comprising the steps of: hooking at least a first prong of the connecting element over an element connected to the gangway; carrying the coupling element to a coupling element at the other vessel or structure; hooking at least a second prong of the connecting element over the said coupling element provided on the other vessel or structure; releasing the first prong from the element connected to the gangway; and moving a free end of the gangway towards the other vessel or structure.
 22. A motion platform for a an assembly according to claim 10, which motion platform comprises at least one carrier for bearing, moving and/or transferring a load, a gangway provided with a first end pivotably connected to the carrier and a second end for contacting a target area, a multiple number of first actuators for moving the carrier relative to the vessel, at least a second actuator for moving the gangway relative to the carrier, a control system arranged for driving the multiple number of first actuators, wherein the control system is also arranged for driving the at least one second actuator, and wherein a cable is provided which is or can be carried at or near the second end of the gangway. 